Virtual reality (VR) and augmented reality (AR) visualization systems are starting to enter the mainstream consumer electronics marketplace. Near-to-eye display (NED) devices, such as head-mounted display (HMD) devices, can be used to display AR or VR content to users. AR devices may include transparent display elements that enable a user to see virtual content transposed over the user's view of the real world. Displayed objects that appear to be superimposed over the user's real-world view are commonly referred to as virtual objects or “holographic” objects. VR and AR visualization systems can provide users with entertaining, immersive three-dimensional (3D) virtual environments in which they can visually (and sometimes audibly) experience things they might not normally experience in real life.
At least some HMD devices include one or more sensors of various types. For example, some HMD devices include sensors such as cameras to facilitate 3D surface mapping, user head-tracking, etc. These cameras generally must be positioned and oriented very precisely in the device in order to provide a satisfactory experience for the user. Yet normal use of the device over time can cause the cameras to move to varying degrees, depending on the design of the device. A challenge in designing an HMD device, therefore, is providing a sensor platform that is easily calibrated in the factory and that maintains a high degree of accuracy over the lifetime of the device. Without those characteristics, an HMD's performance can quickly break down into unpleasant or uncomfortable experiences for the user, where rendered content blends poorly with the user's view of the real world.